Thursday, June 16, 2016

A new REST interface for the Apache CXF Security Token Service - part I

Apache CXF ships a Security Token Service (STS) that can issue/validate/renew/cancel tokens via the (SOAP based) WS-Trust interface. The principal focus of the STS is to deal with SAML tokens, although other token types are supported as well. JAX-RS clients can easily obtain tokens using helper classes in CXF (see Andrei Shakirin's blog entry for more information on this).

However, wouldn't it be cool if a JAX-RS client could dispense with SOAP altogether and obtain tokens via a REST interface? Starting from the 3.1.6 release, the Apache CXF STS now has a powerful and flexible REST API which I'll describe in this post. The next post will cover how the STS can now issue and validate JWT tokens, and how it can transform JWT tokens into SAML tokens and vice versa.

One caveat - this REST interface is obviously not a standard, as compared to the WS-Trust interface, and so is specific to CXF.

1) Configuring the JAX-RS endpoint of the CXF STS

Firstly, let's look at how to set up the JAX-RS endpoint needed to support the REST interface of the STS. The STS is configured in exactly the same way as for the standard WS-Trust based interface, the only difference being that we are setting up a JAX-RS endpoint instead of a JAX-WS endpoint. Example configuration can be seen here in a system test.

2) Issuing Tokens

The new JAX-RS interface supports a number of different methods to obtain tokens. In this post, we will just focus on the methods used to obtain XML based tokens (such as SAML).

2.1) Issue tokens via HTTP GET

The easiest way to get a token is by doing a HTTP GET on "/token/{tokenType}". Here is a simple example using a web browser:

 The supported tokenType values are:
  • saml
  • saml2.0
  • saml1.1
  • jwt
  • sct
A number of optional query parameters are supported:
  • keyType - The standard WS-Trust based URIs to indicate whether a Bearer, HolderOfKey, etc. token is required. The default is to issue a Bearer token.
  • claim - A list of requested claims to include in the token. See below for the list of acceptable values.
  • appliesTo - The AppliesTo value to use
  • wstrustResponse - A boolean parameter to indicate whether to return a WS-Trust Response or just the desired token. The default is false. This parameter only applies to the XML case.
Note that for the "Holder of Key" keytype, the STS will try to get the client key via the TLS client certificate, if it is available. The (default) supported claim values are:
  • emailaddress
  • role
  • surname
  • givenname
  • name
  • upn
  • nameidentifier
The format of the returned token depends on the HTTP application type:
  • application/xml - Returns a token in XML format
  • application/json - JSON format for JWT tokens only.
  • text/plain - The "plain" token is returned. For JWT tokens it is just the raw token. For XML-based tokens, the token is BASE-64 encoded and returned.
The default is to return XML if multiple types are specified (e.g. in a browser).

2.2) Issue tokens via HTTP POST

While the GET method above is very convenient to use, it may be that you want to pass other parameters to the STS in order to issue a token. In this case, you can construct a WS-Trust RequestSecurityToken XML fragment and POST it to the STS. The response will be the standard WS-Trust Response, and not the raw token as you have the option of receiving via the GET method.

3) Validating/Renewing/Cancelling tokens

It is only possible to renew or validate or cancel a token using the POST method detailed in section 2.2 above. You construct the RequestSecurityToken XML fragment in the same way as for Issue, except including the token in question under "ValidateTarget", "RenewTarget", etc. For the non-issue use case, you must specify a "action" query parameter, which can be "issue" (default), "validate", "renew", "cancel".

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